Scientists have found that cigarettes continue to emit harmful compounds even after they have been put out, reports ScienceAlert.

In order to conduct the study, environmental engineer Dustin Poppendieck from the United States National Institute of Standards and Technology (NIST) and his team built a machine that took six puffs per cigarette in an attempt to copy an actual smoker’s behaviour.
The 2,100 recently extinguished cigarettes were then placed inside a chamber made from stainless steel in order to measure the airborne emissions. The team found eight chemicals usually emitted by cigarettes, four of which are on the FDAs list for being harmful or potentially so, according to ScienceAlert.
"I was absolutely surprised. The numbers are significant and could have important impacts when butts are disposed of indoors or in cars," said Poppendieck.